Pain out of proportion to the clinical signs, extreme tenderness but little swelling or erythema does not fit for something common like cellulitis so I would be concerned that cellulitis is not the diagnosis

Fever and tachycardia, I’m not reassured by the normal blood pressure as young patients can maintain their blood pressure even when unwell

Sore throat, tonsillitis and skin and soft tissue infections can be caused by the same bacteria, in particular the Beta-haemolytic Streptococci Groups A, C and G, and the bacteria from a tonsillitis could easily spread to the skin via the blood stream

These are all warning signs for the life-threatening skin and soft tissue infection, necrotising fasciitis. Would you have spotted them?

An hour later the patient becomes hypotensive and the thigh now appears grey and mottled, and is more swollen with a “peau d’orange” appearance (like the skin of an orange, caused by cutaneous oedema). His blood tests come back showing a raised white blood cell (WBC) count and C-reactive protein (CRP) as well as an international normalised ratio (INR) of 1.6.

A thirty five year old, previously fit and well, man presents to the Emergency Department with a painful leg which has come on out of the blue; there is no history of trauma or insect bites. He does say that he had a bit of a sore throat a week ago but that it has now settled. On examination he has a temperature of 39oC and a tachycardia but his blood pressure is normal at 125/75 mmHg. His leg is extremely tender over the lateral aspect of his thigh but there is little to find other than some localised mild swelling with a little overlying erythema.

How would you manage this patient? Are there any “red warning flags” that might make you concerned that this may be more serious than it first appears?

The surgeons are called to see him and decide to immediately take him to theatre for an exploration of the thigh which confirms a diagnosis of necrotising fasciitis.

What is necrotising fasciitis?Necrotising fasciitis is a rapidly progressive, severe life and limb threatening infection involving superficial and deep fascia as well as other tissues. There may be a preceding history of sore throat with Group A Beta-haemolytic Streptococcus and haematogenous seeding.

Necrotising fasciitis due to either Group A Beta-haemolytic Streptococcus or Clostridium perfringens more commonly occurs on a limb when the bacteria settle out in the distal capillaries, whereas synergistic gangrene requires a source of multiple bowel-related bacteria and therefore more commonly occurs in the perineum, pelvis or abdomen.

Clinical Features

Erythema, swelling, heat and pain out of proportion to the other clinical signs leading to discoloration, bullae and eventually gangrene

Systemic features such as fever, hypotension and tachycardia

Pus is NOT usually a feature with Group A Beta-haemolytic Streptococcus; usually only a serosanguinous discharge

Patients with necrotising fasciitis often have blood test results that suggest infection such as raised WBC and CRP. Infections caused by the Group A Beta-haemolytic Streptococcus also have an increased INR because this bacterium produces streptokinase. Monitoring the INR can be used to assess whether the treatment is effective; if the INR does not return to normal the patient still has ongoing infection and needs further surgery.

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Empirical TreatmentThe mainstay of treatment is urgent surgical assessment and tissue resection, which may need to be extensive to reveal healthy tissue.

If there is any doubt as to whether the tissue is viable, it should be removed. Surgeons should have a low threshold for taking patients back to theatre if they are not improving.The choice of antibiotic is based upon the body site affected as this is linked to the most likely causative bacterium. Treatment should be continued for 10-14 days.

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ImmunoglobulinFor Group A Beta-haemolytic Streptococcus and Clostridiumperfringens consider IV Immunoglobulin 2g/kg PLUS a further dose 72 hours after if not improving. This binds the toxin being produced by the bacteria and can help to limit tissue damage, as well as helping to stabilise the patient. It is a large amount of immunoglobulin, and can involve a lot of fluid being infused into the patient which if not carefully monitored can lead to problems with electrolytes and fluid balance. It should be used cautiously.PrognosisNecrotising fasciitis has a high mortality rate (up to 70%) if not managed aggressively enough with surgical intervention; amputation can be a life-saving intervention.

OutcomeThe patient had extensive surgical debridement of the skin, fat and muscle of his thigh. Despite this he needed to go back to theatre several times over the next two days. He remained unconscious and unstable on intensive care as the infection continued to spread up his leg. The surgeons discussed with his wife about the viability of the limb and the need for further surgery. His wife was concerned that as a builder he relies heavily on his physical ability to provide for his family. Ultimately the wife had to face the gravity of the situation and agreed to the amputation of the limb. Two months later the man left the care of the acute hospital and embarked on treatment and therapy for a prosthetic limb; 1 year on he was planning to return to the building trade. This is a positive outcome when up to 70% of patients die from this bacterium more commonly known to cause a sore throat. So would you spot necrotising fasciitis? Bear it in mind next time you see a sick patient with a skin and soft tissue infection where the pain is out of proportion to the clinical signs. By the way, patients don’t usually have a “red warning flag” stuck in them!